Analog or digital information may be communicated to a remote receiver using a variety of communication theory techniques. A typical transmission system includes a transmitter, a communication channel, and a receiver. The transmitter converts the analog or digital information into a form that is suitable for transmission over the communication channel. The receiver recreates the original information from the transmitted signal. The communication channel may be any transmission medium such as wire, optical fiber, or merely free space in which the signals are transmitted as an electromagnetic wave (e.g., radio and television signals).
In a typical wireless communication system, a data signal that includes the information is modulated with a carrier signal and transmitted into free space with an antenna. The receiving system has an antenna and receiver that are tuned to the carrier frequency. The receiving system demodulates the received signal and extracts the data signal. The antenna that is used in the receiving system is usually closely tuned to the carrier frequency.
Technological improvements have made it possible to provide sophisticated functions in portable devices. These portable devices often include wireless communication receivers, transmitters, as well as other functionality such as might be found in personal information managers (PIMS), cellular telephones, personal data assistants (PDAs), palmtop computers, laptop computers, to name a few. Although many of these modern devices include a wireless communication subsystem, the performance of those communication subsystems can be hampered by the physical constraints of the device. For example, limited battery life, poor antenna performance, and in-efficient use of power can yield a weak communication link that results in poor user satisfaction.